MSPs have been told that further increases in the cost of staging the Glasgow 2014 Commonwealth Games will be "very challenging" for the Scottish Government.

Last month, it was revealed that the bill for the sporting event had risen by £81 million to a total of £454 million.

On Wednesday, Caroline Gardner, from the public spending watchdog Audit Scotland, told the politicians: "Any further increase in the budget will be very challenging for the Scottish Government and Glasgow City Council, particularly in the current economic climate."

She warned that with almost five years to go before the Games take place, there were still "significant areas of uncertainty". She also urged all those involved in organising the event to keep the budget under firm control in a bid to prevent future increases.

Ms Gardner, the deputy auditor general, stressed: "We think it is crucial that partners now establish very tight control over the budget to minimise the risk of that happening over the next five years."

The Scottish Government is now contributing £297 million towards the cost of hosting the Games - an increase of £59 million. Glasgow City Council is funding £69 million and the remainder of the £454 million costs will be raised from broadcasting rights, licensing, ticket sales and sponsorship.

Ms Gardner explained to members of Holyrood's Public Audit Committee that the increase in costs came after a detailed review of the Games' budget.

Committee convener Hugh Henry asked if the additional cash was "sufficient to allay the worries" over the costs. Ms Gardner told him: "It is not possible for us to say, though, that there won't be further changes, five years out from the Games there clearly are significant areas of uncertainty."

She told the committee there was a "good chance" the review had identified the most significant areas where costs had changed.

However, she went on: "We know that the world has changed very significantly in terms of the global economic climate. If we are still facing reductions in visitor numbers in 2014 of the scale we have seen this year, then that would have a very significant impact."

Conservatives deputy leader Murdo Fraser said: "Everyone wants to see the Games be a great success but at the same time we're very anxious we keep a tight lid on costs." Meanwhile, former Liberal Democrat leader Nicol Stephen pressed the deputy auditor general on where the additional £59 million of Government funding was coming from.

But Ms Gardner said the details of that had not been included in last month's budget announcement. She told him: "At this stage it's not something we've looked at."

Mr Stephen recalled the Scottish Government had criticised the UK Government for taking cash from other sporting budgets to help meet the costs of the London 2012 Olympics.

He added: "I would be very concerned if the Scottish Government was at the current stage confidentially, without any public scrutiny, pulling funding from sport across other parts of Scotland to invest in the 2014 Games."